CN113366053B - Polylactic acid resin foam sheet, resin molded article, and method for producing polylactic acid resin foam sheet - Google Patents

Abstract

The present invention provides a foamed polylactic acid resin sheet useful for forming a resin molded product that can easily maintain a predetermined shape. More specifically, the present invention provides a foamed polylactic acid resin sheet that contains a crystal nucleating agent and a crystallization accelerator at a predetermined ratio, and is prepared so that the degree of crystallinity becomes a predetermined state.

Description

Manufacturing of polylactic acid resin foam sheets, resin molded products, and polylactic acid resin foam sheets method

technical field

The present invention relates to a polylactic acid resin foam sheet, a resin molded product and a method for manufacturing the polylactic acid resin foam sheet.

This application claims priority based on Japanese Patent Application No. 2019-058551 filed on Mar. 26, 2019, the content of which is hereby incorporated.

Background technique

Conventionally, polyester resin foams are lightweight, have excellent cushioning properties, and are easily molded into various shapes, so they have been used as raw materials for various molded products including packaging materials and the like.

In recent years, countermeasures to the problem of landscape damage due to packaging materials illegally discarded in places such as mountains, rivers, or coasts have been sought.

Against this background, research has been conducted on molded products using polylactic acid resins that are biodegradable in the natural environment, and studies on the development of polylactic acid resin foams for various applications.

For example, a polylactic acid resin foam sheet processed into a three-dimensional shape by thermoforming or the like is used in various applications.

However, polylactic acid resin has crystallinity.

Furthermore, the polylactic acid resin in the crystalline state exhibits higher mechanical strength than the polylactic acid resin in the amorphous state.

Therefore, when producing a resin molded article from a polylactic acid resin, a resin composition containing a crystal nucleating agent and a crystallization accelerator in addition to the polylactic acid resin serving as a base polymer is used.

prior art literature

patent documents

Patent Document 1: Japanese Reexamination No. 2006/121056

Contents of the invention

The problem to be solved by the invention

Like the foamed polylactic acid resin sheet, if it is made by the method of rapid cooling from the hot melt state, the molecules that can be crystallized become present in the sheet in an amorphous state, and the foamed polylactic acid resin sheet When a resin molded product is formed, the resin molded product may be thermally deformed and may not maintain a predetermined shape.

On the other hand, if the foamed polylactic acid resin sheet is formed into a sufficiently crystalline state, it may not be possible to fully exhibit the followability to the molding die during thermoforming or the like, and it may be difficult for the resin molded product to have a predetermined shape from the beginning.

That is, in the conventional foamed polylactic acid resin sheet, there is a problem that it is difficult to form a resin molded product that easily maintains a predetermined shape.

Therefore, an object of the present invention is to provide a foamed polylactic acid resin sheet useful for forming a resin molded product that can easily maintain a predetermined shape, and a method for producing the same, and further provide a resin molded product that can easily maintain a predetermined shape.

solutions to problems

The inventors of the present invention conducted intensive studies to solve the above-mentioned problems, and found that the foamed polylactic acid resin sheet becomes crystals that tend to exhibit good moldability in thermoforming and the like by containing a crystal nucleating agent and a crystallization accelerator in a predetermined ratio. degree, the present invention has been completed so far.

That is, the present invention for solving the above-mentioned problems provides a polylactic acid resin foam sheet,

It contains: polylactic acid resin, crystallization nucleating agent and crystallization accelerator,

With respect to 100 parts by mass of the aforementioned polylactic acid resin, containing 0.5 to less than 3.0 parts by mass of the aforementioned crystallization nucleating agent, and 0.5 to less than 5.0 parts by mass of the aforementioned crystallization accelerator,

The aforementioned polylactic acid resin is not completely crystallized,

The crystallization degree of the said foam seat|seet is 20 % or less, and the said foam seat|seet shows the crystallization degree of 25 % or more by heating.

In addition, the present invention provides a resin molded article comprising part or all of the polylactic acid resin foam sheet described above.

Furthermore, the present invention provides a method for producing a polylactic acid resin foam sheet, which includes an extrusion step: extruding and foaming a resin composition containing a polylactic acid resin together with a foaming agent to produce a polylactic acid resin foam sheet piece,

The production method also includes the following modification step: using an organic peroxide as a free radical initiator to react the polylactic acid resins with each other to prepare a modified polylactic acid resin,

In this modification step, the aforementioned organic peroxide is used in a ratio of 0.1 mass parts to 2 mass parts with respect to 100 mass parts of the aforementioned polylactic acid resin to prepare the aforementioned polylactic acid resin having a melt tension of 5 cN to 40 cN at 190°C. Modified polylactic acid resin,

In the extrusion process, part or all of the polylactic acid resin is the modified polylactic acid resin, and a crystal nucleating agent containing 0.5 parts by mass to less than 3.0 parts by mass is used relative to 100 parts by mass of the polylactic acid resin. The above-mentioned resin composition containing more than 5 parts by mass and less than 5.0 parts by mass of a crystallization accelerator is used to produce the above-mentioned foamed polylactic acid resin sheet.

The effect of the invention

According to the present invention, it is possible to provide a polylactic acid resin foam sheet useful for forming a resin molded product that can easily maintain a predetermined shape, a method for producing the same, and a resin molded product that can easily maintain a predetermined shape.

Description of drawings

FIG. 1 is a schematic diagram showing the configuration of a manufacturing apparatus of a polylactic acid resin foam sheet.

Detailed ways

Embodiments of the present invention will be described below.

Hereinafter, the present invention will be described taking the case where the polylactic acid resin foamed sheet is an extruded foamed sheet produced by an extrusion foaming method as a main example.

The polylactic acid resin foam seat|seet of this embodiment (it may only be called a "foam seat|seet" etc. below) is an extruded foam seat|seet as mentioned above.

That is, the foamed sheet of the present embodiment can be produced by melting and kneading a resin composition containing a polylactic acid resin as a main component together with a foaming agent in an extruder, and passing it through a die attached to the front end of the extruder. Extruded into the atmosphere so it can be crafted.

The polylactic acid resin of the present embodiment is preferably modified to introduce a branched chain structure and a crosslinked structure after the foamed sheet is formed into a good foamed state.

That is, part or all of the polylactic acid resin contained in the resin composition used for extrusion foaming is preferably a modified polylactic acid resin (hereinafter also referred to as "modified polylactic acid resin").

In this embodiment, the polylactic acid resin before modification (hereinafter also referred to as "non-modified polylactic acid resin") used as the raw material of the modified polylactic acid resin may be a homopolymer of lactic acid, or may be a combination of lactic acid and other materials. monomeric copolymers.

Examples of other monomers in the aforementioned copolymer include aliphatic hydroxycarboxylic acids other than lactic acid, aliphatic polyhydric alcohols, aliphatic polyvalent carboxylic acids, and the like.

The aforementioned other monomers may be, for example, polyfunctional polysaccharides or the like.

The lactic acid constituting the aforementioned non-modified polylactic acid resin may be either or both of the L-form and the D-form.

That is, the aforementioned non-modified polylactic acid resin that is the aforementioned homopolymer may be any of poly(L-lactic acid) resin, poly(D-lactic acid) resin, and poly(DL-lactic acid) resin.

Examples of the aliphatic polyhydric carboxylic acid constituting the copolymer include oxalic acid, succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and undecanedioic acid. , dodecanedioic acid, etc.

The aliphatic polycarboxylic acid may also be an anhydride.

Examples of the aforementioned aliphatic polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 3-methyl -1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, neopentyl glycol, tetramethylene glycol, 1,4-cyclohexanedimethanol, etc.

Examples of aliphatic hydroxycarboxylic acids other than lactic acid constituting the copolymer include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 6-hydroxy caproic acid etc.

Examples of the polyfunctional polysaccharides include cellulose, nitrocellulose, methyl cellulose, ethyl cellulose, celluloid, viscose rayon, regenerated cellulose, cellophane, cupro, cupro Rayon, cuprammonium film, ketone ammonia silk, hemicellulose, starch, decolorized pectin (Acropectin), dextrin, dextran, glycogen, pectin, chitin, chitosan, gum arabic, guar gum, locust bean gum, gum arabic, etc.

The non-modified polylactic acid resin in this embodiment preferably contains a structural moiety derived from lactic acid (L-form and D-form) in the molecule at a ratio of 50% by mass or more.

The content of the aforementioned structural moieties (L-body and D-body) is more preferably 60% by mass or more, further preferably 70% by mass or more, particularly preferably 80% by mass or more.

The non-modified polylactic acid resin can be made into a modified polylactic acid resin by reacting the polylactic acid resins with each other using a radical initiator such as an organic peroxide.

The modified polylactic acid resin of the present embodiment is preferably prepared so as to show specific characteristic values in the measurement of melt tension at 190° C. and the measurement of elongational viscosity at the same temperature.

Specifically, the modified polylactic acid resin showed a melt tension of 5 cN or more and 40 cN or less in the melt tension measurement at 190°C.

The melt tension of the modified polylactic acid resin is preferably 39 cN or less, more preferably 37 cN or less, particularly preferably 35 cN or less.

The aforementioned melt tension of the modified polylactic acid resin is preferably 8 cN or more, more preferably 10 cN or more.

The modified polylactic acid resin according to the present embodiment can suppress foam breaking when producing a foam sheet by extrusion foaming using the above-mentioned resin composition because the melt tension is 5 cN or more.

In addition, the modified polylactic acid resin according to the present embodiment has a melt tension of 40 cN or less, so that the cell film exhibits good elongation at the time of foaming, and can suppress foam breaking.

The melt tension measurement at 190°C of the modified polylactic acid resin and the non-modified polylactic acid resin can be measured as follows using a two-hole type capillary rheometer "Rheologic 5000T" (manufactured by CEAST).

(Measuring method of melt tension)

After vacuum-drying each sample at 80°C for 5 hours, it was sealed and stored in a desiccator until immediately before measurement.

Fill the measuring sample resin in a cylinder with a diameter of 15mm heated to a test temperature of 190°C, and after preheating for 5 minutes, pour the sample resin from the capillary mold of the above measuring device (diameter 2.095mm, length 8mm, inflow angle 90 degrees (conical)) Keep the piston lowering speed (0.07730mm/s) constant, and pass the thread-like material through the tension detection pulley located 27cm below the capillary die while extruding it in a linear form, and wind it up with a take-up roller. The speed is an initial speed of 4.0mm/s and an acceleration of 12mm/s ² while gradually increasing the coiling. The average value of the maximum value and the minimum value of the linear object immediately before cutting is taken as the melting tension of the sample.

In addition, when there is only one maximum point in the tension graph, the maximum value is taken as the melt tension.

The modified polylactic acid resin preferably exhibits moderate fluidity when thermally melted, and the melt mass flow rate (MFR) is preferably 0.5 g/10 minutes or more.

The MFR of the modified polylactic acid resin is more preferably 1.0 g/10 minutes or more, still more preferably 1.5 g/10 minutes or more, particularly preferably 2.0 g/10 minutes or more.

The aforementioned MFR is preferably 20 g/10 minutes or less, more preferably 10 g/10 minutes or less, particularly preferably 6.0 g/10 minutes or less.

The melt mass flow rate (MFR) of a modified polylactic acid resin and a non-modified polylactic acid resin can be measured, for example with "melt flow index meter (automatic) 120-SAS" manufactured by Yasuda Seiki Seisakusho Co., Ltd.

MFR is based on b) measurement of piston movement as described in method B of JIS K7210-1:2014 "Plastic - Thermoplastic Melt Mass Flow Rate (MFR) and Melt Volume Flow Rate (MVR) Solution Method - Part 1" Measured by the method of distance and time.

Measurement conditions are as follows.

·Sample: 3~8g

In addition, the sample for measurement was vacuum-dried at 80 degreeC for 5 hours, and it sealed and stored in the desiccator after drying until immediately before measurement.

· Preheating: 300 seconds

·Load hold: 30 seconds

·Test temperature: 190℃

·Test load: 2.16kg (21.18N)

The number of tests of the sample was set to three times, and the average thereof was taken as the value of the melt mass flow rate (g/10 minutes).

When modifying the aforementioned unmodified polylactic acid resin, not only a radical initiator but also a chain extender such as carbodiimide can be used.

In addition, the modification based on the chain extender can use acrylic organic compounds, epoxy organic compounds, isocyanate organic compounds, etc., which have one or more condensation reactions with the hydroxyl and carboxyl groups present in the molecular structure of the polylactic acid resin. Compounds with functional groups.

That is, the aforementioned modification can be performed by a method in which an acrylic organic compound, an epoxy-based organic compound, an isocyanate-based organic compound, or the like is reacted to bond to the polylactic acid resin.

Modification of polylactic acid resins by crosslinking and long-chain branching can be performed by a method of reacting polylactic acid resins with each other using a radical initiator as described above.

In the modification method described above, it is preferable to react the polylactic acid resins with a radical initiator since inclusion of other components in the foam sheet can be suppressed.

It should be noted that if the polylactic acid resins are reacted with each other using a radical initiator with moderate reactivity, the decomposition origin of the polylactic acid resin in the extruder will be attacked by the radicals generated by the radical initiator. , and this site becomes a crosslinking point (branch point) and is stabilized.

Such modification increases thermal stability of the polylactic acid resin, making it difficult to reduce its molecular weight when passing through an extruder.

Examples of the radical initiator used for modification of the polylactic acid resin include organic peroxides, azo compounds, and halogen molecules.

Among them, organic peroxides are preferable.

Examples of the organic peroxide used in this embodiment include peroxyesters, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, peroxyketals, and ketone peroxide, etc.

Examples of the aforementioned peroxyesters include tert-butylperoxy 2-ethylhexyl carbonate, tert-hexylperoxyisopropyl monocarbonate, tert-hexylperoxybenzoate, tert-butylperoxybenzyl ester, tert-butylperoxylaurate, tert-butylperoxy-3,5,5-trimethylhexanoate, tert-butylperoxyacetate, 2,5-dimethyl-2, 5-bis(benzoylperoxy)hexane, tert-butylperoxyisopropyl monocarbonate, and the like.

As said hydroperoxide, peroxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide etc. are mentioned, for example.

Examples of the aforementioned dialkyl peroxides include dicumyl peroxide, di-tert-butyl peroxide, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane Alkyne-3 et al.

Examples of the diacyl peroxide include dibenzoyl peroxide, bis(4-methylbenzoyl)peroxide, and bis(3-methylbenzoyl)peroxide.

As said peroxydicarbonate, bis(2-ethylhexyl) peroxydicarbonate, diisopropyl peroxydicarbonate, etc. are mentioned, for example.

Examples of the aforementioned peroxyketals include 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, 1,1-di-tert-butylperoxycyclohexane, 2 ,2-bis(tert-butylperoxy)butane, n-butyl 4,4-bis(tert-butylperoxy)valerate, and 2,2-bis(4,4-di-tert-butylperoxy Cyclohexyl) propane, etc.

As said ketone peroxide, methyl ethyl ketone peroxide, acetylacetone peroxide, etc. are mentioned, for example.

In the above-mentioned modification by organic peroxide, the modified polylactic acid resin after modification may be caused by the presence of a component with an excessively large molecular weight that becomes a gel when thermally melted, or the decomposition residue of the organic peroxide. Worry about the problem of bad smell.

The above-mentioned organic peroxide is preferably a peroxyester since the occurrence of such problems can be suppressed and the polylactic acid resin can be easily modified to a state suitable for foaming.

In addition, among peroxyesters, the organic peroxide used for modification of the polylactic acid resin is preferably a peroxycarbonate-based organic peroxide such as peroxymonocarbonate or peroxydicarbonate.

In this embodiment, as for the organic peroxide used in the modification of the polylactic acid resin, peroxycarbonate-based organic peroxides are preferably peroxymonocarbonate-based organic peroxides, and tert-butyl peroxide is particularly preferable. Oxyisopropyl monocarbonate.

The above-mentioned organic peroxide also depends on its molecular weight and the like, and usually can be used at a content of 0.1 mass part or more with respect to 100 mass parts of non-modified polylactic acid resin to be modified.

The content of the aforementioned organic peroxide is preferably 0.2 parts by mass or more, particularly preferably 0.3 parts by mass or more.

The content of the organic peroxide is preferably 2.0 parts by mass or less, more preferably 1.5 parts by mass or less, particularly preferably 1.0 parts by mass or less.

Using the organic peroxide at such a content and modifying the non-modified polylactic acid resin makes it possible to make the modified polylactic acid resin suitable for foaming.

When the content of the above-mentioned organic peroxide is 0.1 parts by mass or more, the effect obtained by modifying the polylactic acid resin can be exhibited more reliably.

In addition, when the content of the organic peroxide is 2.0 parts by mass or less, it is possible to suppress the presence of gel mixed in the modified polylactic acid resin.

The polylactic acid resin used in the extrusion foamed resin composition may also be a mixture of modified polylactic acid resin and non-modified polylactic acid resin.

The ratio of the modified polylactic acid resin in the resin composition to the total amount of the polylactic acid resin is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, particularly preferably 90% by mass or more.

The aforementioned resin composition may contain resins other than polylactic acid resin if necessary, but the content of resins other than polylactic acid resin is preferably 10% by mass or less, more preferably 5% by mass or less, further preferably 3% by mass or less.

The resin composition for extrusion foaming preferably contains a crystallization nucleating agent and a crystallization accelerator together with the aforementioned polylactic acid resin.

As said crystal nucleating agent, an organic crystal nucleating agent, an inorganic crystal nucleating agent, etc. are mentioned, for example.

As the aforementioned crystal nucleating agent, only one of an organic crystal nucleating agent and an inorganic crystal nucleating agent may be used, or an organic crystal nucleating agent and an inorganic crystal nucleating agent may be used in combination.

In addition, when only an inorganic crystal nucleating agent is used as the aforementioned crystal nucleating agent, only one of the inorganic crystal nucleating agents listed below may be used, or two or more of them may be used in combination.

Likewise, when only an organic crystal nucleating agent is used as the aforementioned crystal nucleating agent, only one of the organic crystal nucleating agents listed below may be used, or two or more of them may be used in combination.

When using an organic crystal nucleating agent and an inorganic crystal nucleating agent in combination as the aforementioned crystal nucleating agent, either or both of them may be used in plural.

Examples of the inorganic crystal nucleating agent include talc, tin oxide, smectite, bentonite, dolomite, sericite, feldspar powder, kaolin, mica, and montmorillonite.

Among these, talc or tin oxide is preferable as the aforementioned inorganic crystal nucleating agent from the viewpoint of improvement in crystallization speed, heat resistance, durability, and the like.

Examples of the organic crystal nucleating agent include organic amide compounds, organic hydrazine compounds, carboxylate compounds, organic sulfonates, phthalocyanine compounds, melamine compounds, and organic phosphonates.

As the organic sulfonate, various substances such as sulfoisophthalate can be used, and among them, dimethyl 5-sulfoisophthalate metal salt is preferable from the viewpoint of crystallization promoting effect.

Furthermore, barium salts, calcium salts, strontium salts, potassium salts, rubidium salts, sodium salts and the like are preferable.

Examples of the organic amide compound include N,N',N"-tricyclohexyl trimellitic acid amide, N,N'-ethylenebis(12-hydroxystearic acid)amide, and the like.

When the content of the polylactic acid resin contained in the resin composition is 100 parts by mass, the content of the crystal nucleating agent in the resin composition may be, for example, 0.5 parts by mass or more.

The content of the aforementioned crystal nucleating agent in the aforementioned resin composition is preferably 0.6 parts by mass or more, more preferably 0.7 parts by mass or more.

When content of the said polylactic acid resin contained in the said resin composition is 100 mass parts, content of the said crystal nucleating agent in the said resin composition can be made into less than 3.0 mass parts, for example.

The content of the aforementioned crystal nucleating agent in the aforementioned resin composition is preferably 2.5 parts by mass or less, more preferably 2.2 parts by mass or less.

As the aforementioned crystallization accelerator, for example, di-n-octyl phthalate, di-2-ethylhexyl phthalate, dibenzyl phthalate, diisodecyl phthalate, di( Tridecyl) ester, phthalic acid derivatives such as di(undecyl) phthalate, isophthalic acid derivatives such as dioctyl isophthalate, di-n-butyl adipate, hexadiene Adipic acid derivatives such as dioctyl ester, maleic acid derivatives such as di-n-butyl maleate, citric acid derivatives such as tri-n-butyl citrate, itaconic acid derivatives such as monobutyl itaconate, Oleic acid derivatives such as butyl oleate, ricinoleic acid derivatives such as glycerol monoricinoleate, phosphate esters such as tricresyl phosphate and tris(xylyl) phosphate, polyethylene adipate, Hydroxy polycarboxylic acid esters such as polyacrylate acetyl tributyl citrate, polyalcohol esters such as triacetin and tripropionate, polyalkylene glycol derivatives such as polyethylene glycol and polypropylene glycol substances, benzyl/2-(2-methoxyethoxy)ethyl/adipate, polyglycerol fatty acid ester, etc.

As the aforementioned crystallization accelerator, polyglycerin fatty acid ester is preferable.

Examples of the polyglyceryl fatty acid esters include polyglyceryl oleate, polyglyceryl ricinoleate, polyglyceryl laurate, polyglyceryl stearate, polyglycerol condensed ricinoleate, and the like.

Among them, polyglyceryl stearate is preferably used as the aforementioned crystallization accelerator.

Polyglyceryl fatty acid esters can usually be used as plasticizers, which may hinder the crystallization of polylactic acid resins.

However, polyglycerol fatty acid ester has the function of promoting the formation of crystal nuclei of polylactic acid resin, and has the functions of promoting the formation of crystal nuclei and crystallization.

In this embodiment, a modified polylactic acid resin is used as the polylactic acid resin.

That is, the polylactic acid resin in the present embodiment has a molecular structure such as branched chains and crosslinks, and thus crystals are difficult to grow large.

Therefore, it can be said that the polyglycerin fatty acid ester that functions to promote the formation of crystal nuclei without promoting crystal growth is suitable as the crystallization accelerator used in the present embodiment.

When content of the said polylactic acid resin contained in the said resin composition is 100 mass parts, content of the said crystallization accelerator in the said resin composition can be made into 0.5 mass parts or more, for example.

The content of the aforementioned crystallization accelerator in the aforementioned resin composition is preferably 0.6 parts by mass or more, more preferably 0.7 parts by mass or more.

When content of the said polylactic acid resin contained in the said resin composition is 100 mass parts, content of the said crystallization accelerator in the said resin composition can be made into less than 5.0 mass parts, for example.

The content of the aforementioned crystallization accelerator in the aforementioned resin composition is preferably 4.0 parts by mass or less, more preferably 3.5 parts by mass or less.

To the aforementioned resin composition, various additives may be added as necessary.

Examples of such additives include cell regulators, lubricants, antioxidants, antistatic agents, flame retardants, ultraviolet absorbers, light stabilizers, colorants, antibacterial agents, and the like.

In addition, content of the said additive is 10 mass parts or less with respect to 100 mass parts of polylactic acid resins, More preferably, it is 5 mass parts or less.

As the above-mentioned foaming agent used for extrusion foaming together with the above-mentioned resin composition, a physical foaming agent that becomes a gas at normal temperature (23°C) and normal pressure (1 atm), or a decomposition agent that generates gas by thermal decomposition can be used. type foaming agent.

As the aforementioned physical blowing agent, for example, an inert gas, an aliphatic hydrocarbon, an alicyclic hydrocarbon, or the like can be used.

As said inert gas, carbon dioxide, nitrogen, etc. are mentioned, for example.

Examples of the aliphatic hydrocarbons include propane, n-butane, isobutane, n-pentane, and isopentane, and examples of the alicyclic hydrocarbons include cyclopentane and cyclohexane.

In this embodiment, among the above, n-butane and isobutane can be used particularly preferably.

Examples of the above-mentioned decomposable foaming agent include azodicarbonamide, dinitrosopentamethylenetetramine, sodium bicarbonate, or a mixture of organic acids such as citric acid, salts thereof, and bicarbonates, and the like.

It is preferable that the foam seat|seet of this embodiment produced using the above-mentioned resin composition is the state which exhibits some degree of flexibility, considering the followability to the mold surface at the time of molding.

The open cell rate of the foam seat|seet of this embodiment is preferably 10% or more, More preferably, it is 15% or more.

The open cell ratio of the foam seat is preferably 50% or less, more preferably 40% or less, particularly preferably 30% or less, since the foam seat sheet can exhibit excellent strength.

The expansion ratio of the foam sheet is preferably 3 times or more, more preferably 4 times or more, particularly preferably 4.5 times or more.

The expansion ratio of the foam sheet is preferably 15 times or less, more preferably 12 times or less, particularly preferably 10 times or less, since excellent strength can be exhibited.

The open cell rate of a foam seat|seet is measured by the method shown below.

(continuous cell rate)

Cut out a plurality of sheet-shaped samples with a length of 25 mm and a width of 25 mm from the foam sheet, and overlap the cut samples without opening a gap to form a measurement sample with a thickness of 25 mm. Digimatic caliper", the external dimensions of the measurement sample were measured up to 1/100mm, and the apparent volume (cm ³ ) was obtained.

Next, the volume (cm ³ ) of the measurement sample was determined by the 1-1/2-1 air pressure method using an air comparison type hydrometer Model 1000 (manufactured by Tokyo Science Co., Ltd.).

The open cell ratio (%) was calculated from these obtained values and the following formula, and the average value of five test samples was obtained.

It should be noted that the measurement was carried out as follows: After conditioning the sample for 16 hours under the symbol "23/50" of JIS K7100-1999 (temperature 23° C., relative humidity 50%), and a standard atmosphere of Class 2, Under the same standard atmosphere.

In addition, the air comparison type hydrometer is calibrated with a standard ball (large 28.9cc, small 8.5cc).

Continuous cell rate (%)=100×(apparent volume-measured volume under air comparison type hydrometer)/apparent volume

The expansion ratio of the foamed sheet can be obtained as follows: obtain the apparent density (ρ1) of the foamed sheet, obtain the density (true density: ρ0) of the polylactic acid resin composition that constitutes the foamed sheet, and the true density (ρ0) ) divided by the aforementioned apparent density (ρ1), which can be obtained.

That is, the expansion ratio is calculated and obtained by the following formula.

Foaming ratio = true density (ρ0) / apparent density (ρ1)

The density of the said foam seat|seat can be calculated|required by the method described in JISK7222:1999 "foamed plastics and rubber-Measurement of apparent density", Specifically, it measures by the following method.

(Density measurement method)

A sample of more than 100 cm ³ is cut from the foam sheet without changing the original cell structure. For this sample, the symbol "23/50" in JIS K7100:1999 (temperature 23°C, relative humidity 50%), After conditioning for 16 hours in a Class 2 standard atmosphere, the size and mass were measured, and the density was calculated from the following formula.

Apparent density (kg/m ³ ) = mass of sample (kg)/volume of sample (m ³ )

In addition, the size measurement of a sample can use "DIGIMATIC" CD-15 manufactured by Mitutoyo Co., Ltd., for example.

The density of the polylactic acid resin composition can be obtained by performing a test based on the Archimedes method (JIS K8807: 2012 "Density of a solid) on a sample obtained by subjecting a foamed sheet to non-foaming by hot pressing or the like. And the determination of the specific gravity "in the liquid floating amount method) measurement, so as to be able to find out.

The above-mentioned foamed sheet preferably exhibits good moldability when formed into a resin molded product, and the resin molded product exhibits excellent strength after molding. Therefore, for example, it is preferably in a state where crystallization proceeds by heating to a glass transition initiation temperature or higher rather than forming a bubble film. The aforementioned polylactic acid resin was completely crystallized.

It is preferable that the degree of crystallinity is 20% or less at the point that it is easy to give a desired shape by thermoforming etc. about the said foam seat|seet.

The degree of crystallization of the foam sheet is more preferably 19% or less, further preferably 18% or less.

It is preferable that the said foam seat|seet is the state which shows the crystallinity degree of 25 % or more by heating after the resin molded article can exhibit the outstanding strength.

The foam sheet is more preferably in a state of crystallinity of 30% or more by heating to make the resin molded product exhibit excellent strength, and more preferably in a state of crystallinity of 35% or more.

When the degree of crystallinity of the aforementioned foamed sheet is too low, or the degree of crystallization achieved by heating the aforementioned foamed sheet is too high, the change in the degree of crystallization when making a resin molded product becomes large, or the resin molded product sometimes becomes unsatisfactory. fully crystalline state.

From the above, the degree of crystallinity of the foam sheet is preferably 8% or more, more preferably 10% or more, further preferably 12% or more, particularly preferably 14% or more.

The degree of crystallization achieved by heating the foam sheet is preferably 50% or less.

The degree of crystallinity of the foam sheet is more preferably 45% or less, further preferably 40% or less, particularly preferably 38% or less.

The degrees of crystallinity of polylactic acid resins, foamed sheets, and resin molded products are determined as follows.

(degree of crystallinity)

The degree of crystallinity of the polylactic acid resin, the foamed sheet, and the resin molded product was measured with a heat flux differential scanning calorimeter (heat flux DSC) as follows.

The measurement was carried out by the method described in JIS K7122:1987 and JIS K7122:2012 "Measuring method of transition heat of plastics".

Among them, about the sampling method/temperature conditions. Proceed as follows.

5 ± 0.5 mg of the sample was filled to the bottom of an aluminum measurement container (manufactured by Hitachi High-Tech Science Corporation, product number: GAA-0065) so that there was no gap, and then an aluminum lid (manufactured by Hitachi High-Tech Science Corporation) was closed. , product number: GAA-0064), and then, using a differential scanning calorimeter ("DSC7000X, AS-3" manufactured by Hitachi High-Tech Science Corporation), based on a nitrogen flow rate of 20 mL/min, at 30°C for 2 minutes, the following DSC curve when the temperature is raised from 30°C to 210°C at a speed of 2°C/min.

Alumina was used as a reference substance at this time.

Here, the "degree of crystallinity" means: the endothermic heat (heat of fusion (J/g)) obtained from the area of the endothermic peak appearing in crystal melting and the crystallization heat (J/g) obtained from the area of the crystallization peak ( The value obtained by dividing the difference in J/g) by the theoretical heat of fusion (93 J/g) of complete crystallization of polylactic acid.

The heat of fusion and the heat of crystallization were calculated using the analysis software attached to the apparatus.

Specifically, the heat of fusion is calculated from the portion enclosed by the straight line connecting the point where the DSC curve deviates from the low-temperature baseline, the point at which the DSC curve returns to the high-temperature baseline, and the DSC curve.

The heat of crystallization was calculated from the area enclosed by the point where the DSC curve deviates from the low-temperature side baseline, the point where the DSC curve returns to the high-temperature side again, and the straight line connecting the DSC curve.

That is, the degree of crystallinity was obtained by the following formula.

Crystallinity (%)=[heat of fusion (J/g)-heat of crystallization (J/g)]/93(J/g)×100

The above-mentioned heat of fusion (J/g) was obtained by dividing the above-mentioned heat of fusion (J/g) by the theoretical heat of fusion (93 J/g) of complete crystallization of the crystallization degree which the said foam seat|seat can attain by heating.

The degree of crystallinity (%) that the foam sheet can achieve = heat of fusion (J/g)/93(J/g)×100

The degree of crystallization of the foam seat can be adjusted according to the amount of the crystal nucleating agent and the crystallization accelerator used, conditions during extrusion foaming (resin temperature, cooling conditions immediately after extrusion), and the like.

Hereinafter, an example of the manufacturing method of the foam seat|seet of this embodiment is demonstrated.

The manufacturing method of the polylactic acid resin foam seat|seet of this embodiment is equipped with the extrusion process which extrudes and foams the resin composition containing a polylactic acid resin together with a foaming agent, and produces a polylactic acid resin foam seat|seet.

In addition, as described above, this embodiment also includes a modification step of reacting polylactic acid resins with each other using an organic peroxide as a radical initiator to prepare a modified polylactic acid resin.

In the modification step, the organic peroxide is used in a ratio of 0.1 parts by mass to 2 parts by mass with respect to 100 parts by mass of the polylactic acid resin to prepare the aforementioned organic peroxide having a melt tension at 190° C. of 5 cN to 40 cN. Modified polylactic acid resin.

In the extrusion step, part or all of the polylactic acid resin is the modified polylactic acid resin, and the crystal nucleating agent containing 0.5 parts by mass or more and less than 3.0 parts by mass relative to 100 parts by mass of the polylactic acid resin is used, 0.5 mass part or more and less than 5.0 mass parts of the said resin composition of the said crystallization accelerator, the said polylactic acid resin foam sheet|seat is produced.

The aforementioned modification step can be implemented by melt-kneading the non-modified polylactic acid resin and the organic peroxide in a kneader, a twin-screw extruder, or the like.

In this process, the non-modified polylactic acid resin is heated and melted, and the organic peroxide is thermally decomposed to generate free radicals, and the free radicals are used to generate cutting and crosslinking reactions in the molecules of the polylactic acid resin, and the melting is carried out for a predetermined time. By kneading, a modified polylactic acid resin having a branched structure and a crosslinked structure can be obtained.

For the aforementioned modification step, for example, the modified polylactic acid resin can be immediately pelletized using a twin-screw extruder equipped with a pelletizing die (thermal cutting die).

On the twin-screw extruder used in the aforementioned modification process, a strand mold and a T-die are installed. In the aforementioned modification process, the following steps can be additionally implemented: making strands and sheets based on the modified polylactic acid resin, and then , cutting strands, sheets and pelletizing.

In addition, if necessary, the extrusion foaming process can be implemented continuously in a reforming process using a tandem extruder.

In addition, the extrusion foaming process can be implemented continuously in a modification process using a tandem extruder as needed.

For example, the extrusion foaming step in this embodiment can be implemented with the apparatus shown in FIG. 1 .

The apparatus illustrated in FIG. 1 includes a tandem extruder 10 and a circular die CD that discharges the polylactic acid resin composition melt-kneaded by the tandem extruder 10 in a cylindrical form.

Furthermore, the manufacturing apparatus includes: a cooling device CL for air-cooling the foamed sheet discharged from the circular die CD in a cylindrical shape; and a mandrel for expanding the diameter of the cylindrical foamed sheet into a predetermined size. MD; a cutting device that cuts the foamed sheet passing through the mandrel MD into two sheets; and, a roll that is used to make the split foamed sheet 1 pass through a plurality of rollers 21 and take it up Take roll 22.

On the extruder on the upstream side of the aforementioned tandem extruder 10 (hereinafter also referred to as "the first extruder 10a"), there are provided a hopper 11 for feeding polylactic acid resin to be a raw material of the foam sheet, and A gas introduction part 12 for supplying a foaming agent such as hydrocarbon into the barrel.

On the downstream side of the first extruder 10a, an extruder (hereinafter also referred to as "second extruder 10b") for melt-kneading a polylactic acid resin composition containing a foaming agent is provided.

In the case of carrying out the extrusion foaming process in such an apparatus, the modification of the polylactic acid resin is carried out in the first extruder 10a, and at the end of the first extruder 10a or at the base of the second extruder 10b A foaming agent and the like are mixed at the end to prepare a polylactic acid resin composition to be a raw material of a foam sheet, and extrusion foaming can be performed from the aforementioned circular die CD.

The foam seat|seet of this embodiment can prevent that the polylactic acid resin contained in a foam seat|seet crystallizes completely to the state which cannot crystallize more by strengthening the cooling by the cooling device CL.

That is, the foam seat|seat can be produced in the state which suppressed crystallinity low by strengthening the cooling by the cooling device CL.

Moreover, the foam seat|seet of this embodiment can shorten the time from extrusion from circular die CD to reaching mandrel MD, and can manufacture it in the state which suppressed the degree of crystallization low.

In this way, the foamed sheet prepared with a crystallinity of 20% or less is easily deformed by heating, and contains a crystal nucleating agent and a crystallization accelerator in an appropriate ratio, so that rapid crystallization during molding is suppressed. .

Furthermore, in this embodiment, since the polylactic acid resin contained in a foam seat|seet is a modified polylactic acid resin, occurrence of rapid crystallization at the time of molding is suppressed.

Therefore, the foam seat|seet produced in this embodiment shows favorable followability to the molding surface of a molding die, crystallization progresses moderately after molding, and subsequent thermal deformation becomes difficult to generate|occur|produce.

The resin molded article of the present embodiment can be manufactured by processing a foam sheet by a method called thermoforming or the like.

Examples of the aforementioned thermoforming include vacuum forming, pressure forming, vacuum pressure forming, mating die forming, press forming, and the like.

The aforementioned vacuum forming may be an air slide method or a plunger-assisted method.

Furthermore, the resin molded article is preferably heated during molding or in a state where the shape is maintained after molding so that the polylactic acid resin contained is sufficiently crystallized.

Specifically, the resin molded article is preferably prepared so as to have a degree of crystallinity of 0% or more relative to the finally attainable degree of crystallization, and more preferably to be prepared so as to have a degree of crystallization of 90% or more.

The method for producing a resin molded article is not particularly limited to the above-mentioned method.

Moreover, the resin molded article does not need to be formed using only the foam seat|seet of this embodiment, You may form using members other than this foam seat|seet further.

For example, the resin molded product may be one in which a resin film or paper is bonded to the outer peripheral surface of a cup container or a bowl container formed of the foam sheet of the present embodiment.

The foam seat|seet which comprises a part or all of the said resin molded article does not necessarily have to have a three-dimensional shape.

For example, the resin molded product may be composed only of a plate-shaped foam sheet such as a bellows.

The resin molded product in this embodiment is a resin molded product such as a bellows that is easy to be conspicuous only by a slight strain, so that the effect of the present invention can be exhibited more remarkably.

That is, the resin molded article in this embodiment preferably has a plate-shaped foam seatt as a constituent member.

It should be noted that the present invention is not limited in any way by the examples described so far, and the above examples may be appropriately changed.

Example

Hereinafter, although an Example is shown and this invention is demonstrated more concretely, this invention is not limited at all by the following example.

(Example 1)

(modification process)

100 parts by mass of polylactic acid resin ("Biopolymer Ingeo 4032D" manufactured by Nature Works, MFR=4.4g/10min, density=1240kg/m ³ ) and tert-butyl peroxyisopropyl monocarbonate (" Kayacarbon BIC-75", 1-minute half-life temperature T1: 158.8 degreeC) 0.5 mass part was stirred and mixed in the ribbon mixer, and the mixture was obtained.

The obtained mixture was supplied to the twin-screw extruder (L/D=31.5) of diameter 57mm.

Set the set temperature of the feeding part to 170°C, and the subsequent temperature to 230°C. Under the condition of the rotation speed of 150rpm, melt and knead the above-mentioned mixture in the twin-screw extruder, and extrude from the installed A die with a diameter of 3 mm and 18 holes at the front end of the machine extruded the kneaded product in a strand form at a discharge rate of 50 kg/hour.

Next, the extruded strand-shaped kneaded product was passed through a 2-m-long cooling water tank containing water at 30° C., and cooled.

The obtained strand was cut to prepare pellets of a modified polylactic acid resin (mPLA) having a melt tension at 190° C. of 16 cN.

(extrusion process)

The modified polylactic acid resin pellets (mPLA) obtained in the modification step and the crystal nucleating agent (talc: "CROWNTALC" manufactured by Matsumura Sangyo Co., Ltd.) were contained at a mass ratio of 100:1:1 (mPLA:talc:PGFE). ) and a resin composition of a crystallization accelerator (polyglyceryl fatty acid ester (PGFE): "Tirabazole P4" manufactured by Taiyo Chemical Co., Ltd.) was supplied to an extruder, and it was heat-melted and kneaded in this extruder.

Thereafter, butane (isobutane/n-butane=70/30) was injected as a foaming agent into the same extruder, and melt-mixed with the aforementioned resin composition.

Next, this molten mixture was extruded and foamed from a circular die to obtain a cylindrical foam.

For the obtained cylindrical foam, blow the gas along the outer peripheral surface of the mandrel for cooling, and use a gas ring larger than its diameter to blow the gas to the outside, thereby cooling and molding, and cut it with a cutter at one point on the circumference to obtain Ribbon-shaped foam sheet.

The open cell rate of the obtained foam seat|seet was 21 %, and the degree of crystallinity was 17 %.

(Manufacturing of resin moldings)

Prepare a plunger-assisted molding machine equipped with yin and yang bake container shapes (container opening (including ribs) external dimensions: 140mm, bottom external dimensions: 110mm, container depth external dimensions: 35mm) molding dies.

Thermoforming was carried out as follows: set the mold temperature to 120°C, install the foamed sheet obtained above in a molding machine, set the molding cycle to 6.3 seconds, set the temperature of the heater on the cavity side to 290°C, and set the temperature on the plunger side to 290°C. The set temperature of the heater was set to 250° C., and a container (resin molded product) was produced.

(Initial Appearance/Crystallinity of Resin Molded Products)

The container obtained in thermoforming accurately reflects the shape of the molding die.

In addition, the degree of crystallization of the container was measured, and the degree of crystallization was 37%.

(Initial Appearance/Crystallinity/Hot Water Deformation of Resin Molded Products)

Hot water at 100° C. was poured into the obtained container, and after 3 minutes, the hot water was poured out, and the state of expansion of the bottom surface of the container was observed.

Then, when the bottom surface of the container did not appear to be swollen, or the height was less than 3 mm even if swollen, it was judged that the deformation was sufficiently suppressed, and the judgment was "⊚".

In addition, when the swelling height of the bottom surface of the container was 3 mm or more and less than 6 mm, it was judged to be in the allowable range, and the judgment was "◯".

On the other hand, when the swelling height of the bottom surface of the container was 6 mm or more and less than 9 mm, it was judged as "problem" and judged as "Δ".

Furthermore, when the bottom surface of the container swelled by 9 mm or more, it was judged that the deformation was large, and it was judged as "x".

Table 1 shows the above evaluation results.

(Example 2, Comparative Examples 1, 2)

Change the content of crystallization nucleating agent, crystallization accelerator, and change the cooling condition after extrusion foaming, change the degree of crystallization of foam sheet, except that, make foam sheet with the same method as embodiment 1, And a container was produced, and it evaluated similarly to Example 1.

The results are shown in Table 1.

(comparative example 3)

In the foaming step, evaluation was performed in the same manner as in Example 1, except that the non-modified polylactic acid resin pellets were used, and the contents of the crystal nucleating agent and the crystallization accelerator were changed.

However, in Comparative Example 3, there was no melt tension of the resin, and stable collection of the sheet could not be performed, so a foamed sheet could not be obtained.

The results are shown in Table 1.

[Table 1]

As shown in the above table, according to the present invention, a resin molded article that easily maintains a predetermined shape can be obtained.

Claims (3)

1. A polylactic acid resin foam sheet, which comprises: polylactic acid resin, crystallization nucleating agent and crystallization accelerator, 0.5 to less than 3.0 parts by mass of the crystallization nucleating agent and 0.5 to less than 5.0 parts by mass of the crystallization accelerator are contained relative to 100 parts by mass of the polylactic acid resin, The crystal nucleating agent is an inorganic crystal nucleating agent, The crystallization accelerator is polyglycerol fatty acid ester, The polylactic acid resin is not fully crystallized, The degree of crystallization of the foamed polylactic acid resin sheet is not less than 16% and not more than 20%, and the foamed polylactic acid resin sheet is heated to show a degree of crystallization of not less than 25%, The degree of crystallinity of the polylactic acid resin foam sheet is obtained according to the following formula: Crystallinity (%)=[heat of fusion (J/g)-heat of crystallization (J/g)]/93(J/g)×100 The degree of crystallinity shown by heating the foamed polylactic acid resin sheet is obtained according to the following formula: Crystallinity (%)=heat of fusion (J/g)/93(J/g)×100. 2. A resin molded article comprising part or all of the foamed polylactic acid resin sheet according to claim 1. 3. a manufacture method of polylactic acid resin foamed sheet, it possesses following extruding process: the resin combination that comprises polylactic acid resin is carried out extrusion foaming together with blowing agent, makes polylactic acid resin foamed sheet, The production method also includes the following modification step: using an organic peroxide as a free radical initiator to react the polylactic acid resins with each other to prepare a modified polylactic acid resin, In this modification step, the organic peroxide is used in a ratio of 0.1 parts by mass to 2 parts by mass with respect to 100 parts by mass of the polylactic acid resin, and the melt tension at 190° C. is 5 cN to 40 cN. The modified polylactic acid resin, In the extrusion process, a part or all of the polylactic acid resin is the modified polylactic acid resin, and a crystal nucleating agent containing 0.5 parts by mass to less than 3.0 parts by mass is used relative to 100 parts by mass of the polylactic acid resin. agent, 0.5 mass parts or more and less than 5.0 mass parts of the resin composition of the crystallization accelerator, making the polylactic acid resin foam sheet, The crystal nucleating agent is an inorganic crystal nucleating agent, The crystallization accelerator is polyglycerol fatty acid ester, The degree of crystallization of the foamed polylactic acid resin sheet is more than 16% and less than 20%, and the degree of crystallization of the foamed polylactic acid resin sheet is obtained according to the following formula: Crystallinity (%)=[heat of fusion (J/g)-heat of crystallization (J/g)]/93(J/g)×100.